This invention relates to printing and, in particular, to the process of offset printing where waterless lithographic plates may be used.
There are many different types of printing, but one of the more popular processes is known as offset lithography where a plate having inked image areas and ink repelling (i.e., non-inked) non-image areas is used. The non-image areas are treated with water using a system of dampening rolls, and the water repels the ink so as to form the non-inked area. The ink is distributed to the plate cylinder via its own set of rollers that define an inking system which break down, vibrate and generally distribute the ink.
Recently a waterless silicone plate has been developed for use in offset systems and as a substitute for the water-based system (i.e., eliminates the use of the dampening system). The plate defines a series of ink-receiving wells or impressions that define the imaging area and the non-imaging area is defined by a silicone rubber layer between the ink receiving imaging areas. The silicone rubber repels the ink and thus only the inked areas are the image areas.
In water-based systems, water or a water-alcohol solution (sometimes substitutes are provided for the alcohol and other additives such as ethylene glycol may be used) is used to provide the ink repelling non-imaging area. The water and alcohol also provide some temperature control for the printing process in general and the ink specifically. In order to function properly, when the ink is applied, usually by the blanket cylinder to the substrate, the ink must be held within a predetermined temperature range.
Thus it is an object of this invention to provide a temperature regulation system for use in a press using a waterless plate to maintain the ink temperature, particularly at the time and place of application, within a predetermined temperature range.
Regular commercially available lithographic inks are used in the water-based system, but more expensive and specially compounded inks are provided for in the waterless system.
Moreover, a plurality of inks of different colors may be used, each requiring maintenance within its own predetermined temperature range and each temperature range may be different.
Thus it is another object of this invention to provide a temperature regulation system for use in a press using a waterless plate to maintain the temperature of each ink within the ink's predetermined operating temperature range.
Current offset presses utilize a cooling or refrigeration system and heater or Kcal rods associated with inking rolls, usually the vibrator rolls, for controlling the temperature of the rolls. This system has been found not to provide an effective system, particularly for use in a waterless system as it operates only at a discrete high temperature and a discrete low temperature and not continuously therebetween. Moreover, the response time or the rate at which the system can adjust to a temperature can be prolonged, particularly as the prior art system uses heating rods to raise the temperature of the temperature regulating fluid flowing to ink rolls. Furthermore, the use of Kcal rods can be very consumptive of energy. All of these deficiencies can affect the ultimate printed product.
Thus it is yet another object of this invention to provide a temperature regulating system for use with an offset press, particularly using a waterless plate so as to effectively control ink temperature and overcome problems of the prior system.
At present there is a significant installed base of water-based offset lithographic systems. Thus, it is anticipated that water-based offset lithographic systems will continue to be used in significant numbers. Thus sometimes a press may selectively be used for water-based or waterless printing.
Thus it is an object of this invention to utilize the temperature regulation system developed for the water-less system also with water-based systems.
These and other objects of this invention will become apparent from the following disclosure and appended claims.